Processes connected with deactivation of the metal catalysts (Pd, Ni and Cu, Ag) by carbon deposits have been investigated by the computer simulation methods. (i) The simulations of the metal surfaces for different coverage of the surface by carbon atoms have been performed by the Molecular Dynamics method. (ii) The Potential Energy Surfaces for the binding energy of a carbon atom in contact with metal surfaces have been calculated by quantum DFT methods. It was found that the carbon atom blocks the diffusion paths of the H and O atoms on the metal surface. (iii) The surface reactions of C atom with CO2 molecules and O or H atoms have been simulated on a microscopic quantum level. It was shown that some of these processes remove the carbon deposit from the metal surface.